The present invention relates to a metal cylinder head gasket with a partial support portion around a hole to be sealed.
An internal combustion engine has been developed to provide light weight and high power. For this purpose, a cylinder head is made of light metal or alloy thereof, such as aluminum alloy. The rigidity of the cylinder head made of light metal or alloy is not so strong. On the other hand, since a metal gasket is strong against high temperature and pressure, the metal gasket has now been used widely as a cylinder head gasket.
In case the cylinder head as stated above is attached to a cylinder block with the metal gasket therebetween, since the rigidity of the cylinder head is not so strong, the edge portions, especially longitudinal end portions of the gasket are liable to be strongly compressed. Extremely speaking, a center area of the cylinder head projects upwardly.
Also, when the engine as explained above is actuated, the edge portions vibrate severely. In case a sealing bead is located at the edge portion, the sealing bead is beaten by the cylinder head to cause creep relaxation. Thus, fluid leakage may happen in a long usage.
Namely, in the engine, the gasket edge portions receive strong pressure when the gasket is tightened. Also, the gasket edge portions are likely to vibrate.
In order to support tightening pressures at the gasket edge portions and reduce the vibration, various proposals have been made. For example, support beads are formed at the gasket edge portions, as disclosed in U.S. Pat. No. 5,427,389. Also, support beads are formed around the cylinder bores located at the longitudinal side portions, as disclosed in U.S. Pat. No. 5,439,234. Further, shims are disposed at the lateral side portions of the gasket, as disclosed in U.S. Pat. No. 5,538,263.
On the other hand, in the metal gasket, a bead is often formed around a hole to be sealed. When the bead is compressed, the bead provides a surface pressure to seal around the hole. In case the bead is substantially flattened when the gasket is installed in the engine, the bead may creep in a long usage. Thus, a flange or solid portion may be formed inside the bead, or a surface pressure regulation plate may be disposed outside the bead so that the bead is not completely flattened.
The above conventional gaskets operate properly, as intended. However, the above gaskets can not solve all the problems, and there arise problems to be solved.
One object of the invention is to provide a metal cylinder head gasket, which can support a part of a pressure applied to the gasket.
Another object of the invention is to provide a metal cylinder head gasket as stated above, wherein creep relaxation of sealing means formed around a hole is prevented.
A further object of the invention is to provide a metal cylinder head gasket as stated above, wherein the sealing means can be compressed as equal as possible.
Further objects and advantages of the invention will be apparent from the following description of the invention.